JP7246861B2 - Cement manufacturing equipment, cement manufacturing method, design method for cement manufacturing equipment - Google Patents

Description

The present invention provides a cement production apparatus equipped with a carbon dioxide production apparatus for producing high-concentration carbon dioxide by heating cement raw material refinement, limestone, etc., using heat generated in the cement production apparatus, cement production, for example. methods and methods for designing cement production equipment.

In recent years, attempts to reduce carbon dioxide (CO ₂ ), which is the main cause of global warming, have been promoted worldwide and across all industries. For example, the cement industry is one of the industries that emit a large amount of carbon dioxide, along with electric power, steel, etc., and accounts for about 4% of the total carbon dioxide emissions in Japan. For this reason, it has been considered to recover the exhaust gas containing carbon dioxide generated in the cement manufacturing process without releasing it into the atmosphere.

The recovered carbon dioxide can be reused in a wide range of ways, such as storage in the ground, cultivation of plants and algae, and use as liquid carbonic acid for food raw materials and industrial raw materials. On the other hand, in order to effectively use the recovered carbon dioxide industrially, it is necessary to increase the concentration of carbon dioxide to a high concentration such as 95 to 100 vol %. For example, the carbon dioxide contained in the exhaust gas generated in the cement manufacturing process includes not only carbon dioxide generated by burning coal, petroleum coke, and combustible waste, but also carbon dioxide generated from limestone contained in cement raw material refinement. Although it is higher than the combustion gas of , its concentration is about 20 vol %. In addition, when the recovered carbon dioxide is used for growing plants and algae or as a raw material for food, it is important that it does not contain harmful components.

A concentration method for increasing the concentration of carbon dioxide includes, for example, an amine absorption method. In the amine absorption method, a gas containing carbon dioxide is brought into contact with an alkaline aqueous solution (absorption liquid) such as amine to selectively absorb carbon dioxide, and then the absorption liquid is heated to separate the high-concentration carbon dioxide. , is to be collected. However, concentrating carbon dioxide to a high concentration by the amine absorption method requires a large amount of absorbent, which is costly, and has not yet been put to practical use as a method for concentrating carbon dioxide generated in the cement manufacturing process.

In addition, in cement kilns and calciners of cement manufacturing equipment, when using exhaust gas containing carbon dioxide obtained by burning thermal energy such as coal, oil, natural gas with pure oxygen, this exhaust gas contains combustion gas It contains volatile organic compounds (VOCs), carbon monoxide, nitrogen oxides, sulfur oxides, and other impurities that are harmful to humans and plants. Therefore, when the obtained exhaust gas containing carbon dioxide is stored underground or used for growing plants and algae or as a raw material for food, it is necessary to increase the concentration of carbon dioxide by removing these impurities. As a method for concentrating , the cost is high, and it has not yet been put into practical use.

On the other hand, Patent Document 1 describes a method of recovering high-concentration carbon dioxide by indirectly heating carbon dioxide generated from limestone contained in cement raw material refined powder. This is done by heating cement raw material refinement through a partition wall, or by contacting a heat medium such as overheated calcined cement raw material with the exhaust gas containing carbon dioxide generated during calcining to remove high concentrations of carbon dioxide. is the way to get

JP 2009-269785 A

According to the method for recovering carbon dioxide in a cement production facility disclosed in Patent Document 1, it is possible to recover high-concentration carbon dioxide, such as 100 vol %, from exhaust gas generated during cement production. However, the higher the concentration of carbon dioxide to be recovered, the higher the reaction temperature, which increases the cost required for heating. Therefore, there is a demand for a method for producing carbon dioxide that is capable of producing high-concentration carbon dioxide at a lower reaction temperature at low cost.

The present invention has been made in view of the circumstances described above, and is a cement production apparatus equipped with a carbon dioxide production apparatus capable of producing high-concentration carbon dioxide containing almost no harmful components at low cost, and An object of the present invention is to provide a cement manufacturing method and a method for designing a cement manufacturing apparatus using the same.

In order to solve the above problems, the cement production apparatus of the present invention includes a carbon dioxide production apparatus, a calciner and a cement kiln, and the carbon dioxide production apparatus includes a gas circulation line for circulating a gas containing carbon dioxide. , a heat exchanger, a reactor, and a separator arranged in order in the gas circulation line; a raw material powder supply line, a carbon dioxide recovery line, and a reaction temperature lowering means connected to the gas circulation line; The heat exchanger exchanges heat between the gas circulation line and a high-temperature atmosphere field having a temperature higher than the temperature of the gas circulation line, and the raw material powder supply line exchanges heat with the reactor. or connected to the reactor, introducing raw material powder for producing carbon dioxide into the gas circulation line, and the reactor converts the carbon dioxide-containing gas heated by the heat exchanger into The raw material powder is brought into contact to produce carbon dioxide by a decarboxylation reaction, the separator separates the raw material powder and the carbon dioxide-containing gas, and the reaction temperature lowering means reduces the reaction temperature. The reaction temperature of the decarboxylation reaction in the reactor is lowered by a decompression pump that decompresses the vessel, and the carbon dioxide recovery line passes the gas containing carbon dioxide having a carbon dioxide concentration of 95 vol% or more to the gas circulation line. The calciner heats the raw material powder separated by the separator, and the cement kiln heats the raw material powder heated in the calciner to produce cement. It is characterized by generating clinker .

Further, the present invention further comprises a clinker cooler, a preheater, and a bleed duct connecting the clinker cooler and the calciner, and the high-temperature atmospheric field is the cement kiln, the clinker cooler, and the preheater in the cement manufacturing apparatus. It is preferable to include at least one of the heater, the calciner, and the extraction duct.

A cement manufacturing method of the present invention is a cement manufacturing method using the cement manufacturing apparatus according to each of the above items, comprising: a heating step of heating the gas containing carbon dioxide in the heat exchanger in the high-temperature atmosphere field; a reaction step in which the raw material powder is brought into direct contact with the gas containing carbon dioxide heated in the heating step and heated to cause a decarboxylation reaction to produce carbon dioxide; A solid-gas separation step for separating a gas containing carbon, an amount of the gas containing carbon dioxide corresponding to the amount of carbon dioxide generated in the reaction step is recovered, and the remaining gas containing carbon dioxide is separated from the gas A recovering step of returning to a circulation line, a calcining step of heating the raw material powder separated in the solid-gas separation step in the calcining furnace, and a raw material powder heated in the calcining step. and a cement clinker producing step of heating in the cement kiln to produce cement clinker .

Further, in the present invention, in the reaction step, based on the internal pressure of the gas circulation line and the temperature of the gas containing carbon dioxide after being heated by the heat exchanger, the amount of carbon dioxide produced is a maximum value of ±10 %, it is preferable to control the reaction pressure in the decarboxylation reaction and the supply amount of the produced raw material powder to the gas circulation line.

Further, in the present invention, it is preferable that in the reaction step, the reaction pressure of the decarboxylation reaction is reduced to less than atmospheric pressure by the reaction temperature lowering means.

The method for designing a cement manufacturing apparatus of the present invention is the method for designing a cement manufacturing apparatus according to each of the above items, wherein the internal pressure of the gas circulation line and the temperature of the gas containing carbon dioxide after being heated in the heating step Based on this, the reaction pressure in the decarboxylation reaction and the supply amount of the generated raw material powder to the gas circulation line are determined so as to maximize the amount of carbon dioxide produced, and based on this determination, the carbon dioxide It is characterized by designing a carbon production device.

INDUSTRIAL APPLICABILITY According to the present invention, a cement manufacturing apparatus equipped with a carbon dioxide manufacturing apparatus capable of manufacturing high-concentration carbon dioxide containing almost no harmful components at low cost, a cement manufacturing method using the same, and a cement manufacturing apparatus can provide a design method for

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the cement manufacturing apparatus in which the carbon dioxide production apparatus of 1st Embodiment of this invention and this carbon dioxide production apparatus are installed. It is a schematic diagram which shows an example of a 1st heat exchanger. It is a schematic diagram which shows an example of a reactor. 1 is a graph showing the equilibrium vapor pressure curve of carbon dioxide in the decarboxylation reaction of CaCO ₃ , which is the main component of limestone. BRIEF DESCRIPTION OF THE DRAWINGS It is the flowchart which showed the carbon dioxide production method of this invention step by step. It is a graph which shows the relationship between the carbon dioxide production amount and the limestone input amount. It is a graph which shows the relationship between a limestone reaction rate and the amount of carbon dioxide production. It is a graph which shows the relationship between a limestone reaction rate and the amount of limestone input. It is a graph which shows the relationship between post-reaction temperature and a limestone reaction rate. It is a graph which shows the relationship between the carbon dioxide temperature and the carbon dioxide flow rate under constant enthalpy. It is a graph which shows the calculation example which plotted the relationship between the maximum amount of carbon dioxide production and the amount of limestone input at that time for each temperature and (R/L) of carbon dioxide. 4 is a graph showing a calculation example in which the relationship between the maximum amount of carbon dioxide produced and the amount of limestone input at that time is plotted for each temperature and flow rate of carbon dioxide and reaction pressure. 13 is an enlarged view of a main portion of the graph of FIG. 12; FIG. 14 is an explanatory diagram in which the rectangular area shown in FIG. 13 is further divided into 10 equal parts; FIG. It is a graph which shows the relationship between the limestone input amount and the production amount of carbon dioxide. It is a graph which shows the relationship between the limestone input amount and the production amount of carbon dioxide.

A carbon dioxide production apparatus and a carbon dioxide production method using the same according to an embodiment of the present invention will be described below with reference to the drawings. It should be noted that each embodiment shown below is specifically described for better understanding of the gist of the invention, and does not limit the invention unless otherwise specified. In addition, in the drawings used in the following description, in order to make it easier to understand the features of the present invention, there are cases where the main parts are enlarged for convenience, and the dimensional ratio of each component is the same as the actual one. not necessarily.

(Carbon dioxide production equipment)
First, the configuration of the cement production apparatus that serves as the supply source of the raw material powder and the high-temperature atmosphere field in the carbon dioxide production apparatus of the present invention will be described.
FIG. 1 is a schematic diagram showing a carbon dioxide production apparatus according to a first embodiment of the present invention and a cement production apparatus in which this carbon dioxide production apparatus is installed.
In the following description, high-concentration carbon dioxide is assumed to be used as a raw material for liquefied carbonic acid, for example, and the concentration range is 90% or more and 100% or less, preferably 95% or more and 100% or less. Desirably, it is 98% or more and 100% or less. In FIG. 1, solid line arrows indicate the flow of gas such as carbon dioxide-containing gas, and dotted line arrows indicate the flow of solids (powder) such as raw material powder.

A cement manufacturing apparatus 30 shown in FIG. The cement manufacturing apparatus 30 shown in FIG. 1 is configured to perform a calcination process, which is an essential part of the cement manufacturing process. (not shown) is provided, and a clinker crusher and a classifier (not shown) are provided in the finishing process, which is a post-sintering process.

The preheater 31 is composed of a plurality of stages of cyclones 31A to 31D arranged in the vertical direction and connected to each other. there is In addition, in this embodiment, the two sets of preheaters 31, 31 are arranged in parallel with each other. Only one set of preheaters 31 may be provided, or three or more sets may be provided.

A cement raw material supply line 42 is connected to the uppermost cyclone 31A, and cement raw material refined powder M is supplied to the uppermost cyclone 31A through this cement raw material supply line 42 from the raw material process, which is the previous process. The refined cement powder M is mainly composed of powdered limestone (CaCO ₃ ), and also contains clay components (SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ ) and the like.

On the other hand, the high-temperature exhaust gas C1 discharged from the calcining furnace 34 is supplied to the lowermost cyclone 31D and flows toward the uppermost cyclone 31A. Then, the exhaust gas C1 that has reached the uppermost cyclone 31A is exhausted through the exhaust line 36 by the exhaust fan 35 .

The refined cement powder M supplied to the uppermost cyclone 31A is preheated by the high-temperature exhaust gas C1 flowing toward the uppermost cyclone 31A as it sequentially falls to the lower cyclones 31B and 31C. The cement raw material refined powder M that has reached the lower cyclone 31C is heated to, for example, about 750° C., and then sent to the calciner 34 via the raw material pipe 37 . The cement raw material refined powder M is further heated to about 850° C. in this calciner 34 by a coal burner 34a.

A raw material powder supply line 21 that is connected to a gas circulation line 11 of a carbon dioxide production apparatus 10, which will be described later, branches off from the middle of the raw material pipe 37 . Part of the raw material refined powder M discharged from the lower cyclone 31C enters the raw material powder supply line 21, and the cement raw material refined powder M after calcination is supplied to the gas circulation line 11 of the carbon dioxide production device 10. supply.

The cement raw material refined powder M heated by the calcining furnace 34 is returned to the preheater 31 again through the calcining furnace exhaust duct 38, and is discharged from the lowermost cyclone 31D through the transfer pipe 39 to the kiln end of the cement kiln 32. It is sent to the section 32a.

The cement kiln 32 includes, for example, a rotatable cylindrical furnace body 32b and a main burner 32c that heats the inside of this furnace body 32b. The preheated refined cement raw powder M introduced from the kiln bottom 32a is heated by the main burner 32c inside the furnace body 32b.

The cement raw material refined powder M heated to, for example, about 1450° C. in the cement kiln 32 undergoes reactions represented by the following formulas (1) to (5).
CaCO ₃ →CaO+CO ₂ (1)
3CaO+SiO ₂ →3CaO·SiO ₂ (2)
2CaO+SiO ₂ →2CaO·SiO ₂ (3)
3CaO+Al ₂ O ₃ →3CaO.Al ₂ O ₃ (4)
_{4CaO + Al2O3} + _{Fe2O3 → 4CaO.Al2O3.Fe2O3} ( _{5 )}
As a result, alite (3CaO.SiO ₂ ) and belite (2CaO.SiO ₂ ), which are calcium silicate compounds finally constituting cement clinker, and an aluminate phase (3CaO.Al ₂ O ₃ ), which is an interstitial phase. and a ferrite phase (4CaO.Al ₂ O ₃ .Fe ₂ O ₃ ) is produced.

The clinker cooler 33 is composed of, for example, a cooling fan, and cools the high-temperature cement clinker produced in the cement kiln 32 . The cement clinker thus cooled is further pulverized and classified into cement in the finishing process.

On the other hand, the high-temperature extraction gas C2 generated when the high-temperature cement clinker is cooled in the clinker cooler 33 is sent to the calcination furnace 34 through the extraction duct 41 connecting the clinker cooler 33 and the calcination furnace 34. . This bleed gas C2 is heated to about 800 to 1000° C., for example. In this embodiment, the extraction duct 41 constitutes a high-temperature atmosphere field H in the carbon dioxide production apparatus 10, which will be described later.

Next, the configuration and action of the carbon dioxide production apparatus of the present invention will be described. The carbon dioxide production apparatus 10 includes a gas circulation line 11 for circulating a gas G containing carbon dioxide, a first heat exchanger (heat exchanger) 12, a reactor 13, and a separation , a raw material powder supply line 21 connected to the gas circulation line 11 , a carbon dioxide recovery line 22 , and a reaction temperature lowering means 23 . A second heat exchanger 15 and a circulation pump 16 are further arranged in the gas circulation line 11 .

The gas circulation line 11 is a gas flow path through which the gas G containing carbon dioxide flows, and is formed in an annular shape to circulate the gas G containing carbon dioxide. In FIG. 1, gas G containing carbon dioxide circulates counterclockwise. In addition, through a part of the gas circulation line 11, refined raw cement powder M, which is raw powder to be produced, which will be described later, also flows. In addition, the concentration of carbon dioxide in the gas G containing carbon dioxide flowing through the gas circulation line 11 is not necessarily uniform throughout the gas circulation line 11, and the concentration of carbon dioxide may differ depending on the section. In this embodiment, the concentration of carbon dioxide contained in the gas G containing carbon dioxide flowing through the gas circulation line 11 is in the range of 95 vol % or more and 100 vol % or less.

The gas circulation line 11 is made of a material that can withstand a high temperature environment, for example, a temperature of 800° C. or higher, such as silicon carbide, alumina, zirconia, or a material containing them. Furthermore, among these materials, it is more preferable to use materials with low reactivity to limestone. Note that the portion of the gas circulation line 11 where the first heat exchanger 12 and the reactor 13 are formed may be made of a material that can withstand a higher temperature of about 850.degree.

The first heat exchanger 12 (heat exchanger) exchanges heat between the gas G containing carbon dioxide flowing through the gas circulation line 11 and the high-temperature atmosphere field H, that is, the high-temperature extraction gas C2 flowing through the extraction duct 41. conduct. The high-temperature atmosphere field H is set to a temperature higher than the temperature of the gas circulation line 11 on the side flowing into the first heat exchanger 12 . For example, the temperature of the gas circulation line 11 at the portion entering the first heat exchanger 12 is about 600.degree. C., and the high-temperature atmosphere field H is about 900.degree. By exchanging heat with such a high-temperature atmosphere field H, the gas G containing carbon dioxide flowing through the gas circulation line 11 is heated to about 850° C., for example.

FIG. 2 is a schematic diagram showing an example of the first heat exchanger.
The first heat exchanger 12 is formed in the extraction duct 41 of the cement manufacturing apparatus 30, which is an example of the high-temperature atmosphere field H, in this embodiment. Inside the extraction duct 41, a high temperature extraction gas C2 of about 800 to 1000° C., for example, flows from the clinker cooler 33 toward the calciner .

The first heat exchanger 12 has a double-tube structure including an inner tube 12a and an outer tube 12b, and the gas G containing carbon dioxide flowing into the first heat exchanger 12 flows inside the inner tube 12a. , flows out from the end of the inner tube 12a into the outer tube 12b, and further flows between the inner tube 12a and the outer tube 12b. In the first heat exchanger 12, the gas circulation line 11 is composed of a channel for the carbon dioxide-containing gas G, which is composed of an inner tube 12a and an outer tube 12b.

The inner tube 12a and the outer tube 12b that constitute the first heat exchanger 12 are made of silicon carbide (SiC), for example. Even in a high temperature environment of about 1000 ° C., silicon carbide is burned by gas G containing carbon dioxide, preheater 31 of cement manufacturing apparatus 30, cement kiln 32, clinker cooler 33, calciner 34, etc. It has excellent corrosion resistance against gases containing impurities such as volatile organic compounds (VOC) derived from gases, carbon monoxide, nitrogen oxides, sulfur oxides, etc., and also has excellent thermal conductivity. According to the first heat exchanger 12 having such a configuration, heat exchange can be efficiently performed over a long period of time between the gas G containing carbon dioxide and the extraction gas C2.

Referring to FIG. 1 again, in the present embodiment, the high-temperature atmospheric field H that exchanges heat with the gas circulation line 11 in the first heat exchanger 12 includes the clinker cooler 33 and the calciner 34 in the cement manufacturing apparatus 30. However, the high-temperature atmosphere field H is not only inside the bleed duct 41, but also in high-temperature parts of the cement manufacturing apparatus 30, such as the cement kiln 32 and the clinker At least one of the cooler 33, the preheater 31, and the calcining furnace 34 may be used.

To the reactor 13 on the downstream side of the first heat exchanger 12 in the gas circulation line 11 is connected a raw material powder supply line 21 for supplying refined cement raw material powder M, which is raw material powder for producing carbon dioxide. This raw material powder supply line 21 supplies the cement raw material refined powder (produced raw material powder) M heated to, for example, about 750° C. by the preheater 31 of the cement manufacturing apparatus 30 to the reactor 13 . The cement raw material refined powder M supplied from the raw material powder supply line 21 directly contacts the gas G containing carbon dioxide heated by the first heat exchanger 12 in the reactor 13 to cause a decarboxylation reaction.

In this embodiment, the raw material powder supply line 21 is configured to be connected to the reactor 13, but in addition to this, for example, between the first heat exchanger 12 and the reactor 13 ( It may be connected to the upstream side of the reactor 13). Further, the carbon dioxide-generating raw material powder may be high-purity limestone powder or the like in addition to the cement raw material refined powder M.

FIG. 3 is a schematic diagram showing an example of a reactor.
The reactor 13 includes, for example, a tubular reaction container 25 . For example, the reaction vessel 25 may be a reaction tube having a diameter larger than that of the piping constituting the gas circulation line 11 in order to increase the residence time of the gas G and promote the reaction. The reaction vessel 25 constitutes a part of the gas circulation line 11, and the gas G containing carbon dioxide heated by the first heat exchanger 12 flows from one end 25a toward the other end 25b. A raw material powder supply line 21 is connected to one end 25a of the reaction vessel 25, and cement raw material refined powder M is supplied into the reaction vessel 25 at a predetermined flow rate.

In the reaction vessel 25, the reactor 13 reacts with the carbon dioxide-containing gas G heated to about 850°C by the first heat exchanger 12, and the cement raw material refined powder heated to about 750°C by the preheater 31. By contacting M, the refined cement raw powder M is heated to decarboxylate limestone (CaCO ₃ ), which is the main component of the refined cement raw powder M (thermal decomposition reaction: see formula (6) below). cause
CaCO ₃ →CaO+CO ₂ (6)

It should be noted that the decarboxylation reaction is not necessarily completed in the reactor 13 for the entire amount of the cement raw material refined powder M that is input. The decarboxylation reaction may occur in some cases, and the region where the decarboxylation reaction occurs is not limited.

In the reactor 13 (and the entire gas circulation line 11 including this), the reaction temperature lowering means 23 provided in the middle of the carbon dioxide recovery line 22 connected to the gas circulation line 11 lowers the reaction temperature at which the decarboxylation reaction occurs. The lower limit is lowered. Specifically, in this embodiment, the reaction temperature lowering means 23 is composed of a decompression pump 24 , and the entire gas circulation line 11 including the reactor 13 is decompressed by the decompression pump 24 .

Here, limestone in a space filled with high-concentration carbon dioxide with a concentration range of 90% or more and 100% or less, preferably 95% or more and 100% or less, more preferably 98% or more and 100% or less The reaction temperature is defined as the temperature at which decarboxylation of (CaCO ₃ ) occurs. In the following description, when we refer to reaction temperature, we mean the temperature defined above.

Figure 4 is the equilibrium vapor pressure curve of carbon dioxide in the decarboxylation reaction of _CaCO3 , the main component of limestone. According to the graph shown in FIG. 4, the lower the reaction pressure, the lower the reaction temperature. For example, when the pressure is 1 atm, the limestone decarboxylation reaction shown in formula (4) does not proceed unless the temperature is 893° C. or higher. On the other hand, when the pressure is 0.33 atm and the temperature is 823° C. or higher, the decarboxylation reaction of limestone shown in the formula (4) proceeds. Therefore, by reducing the pressure in the reactor 13, the reaction temperature can be lowered. In this embodiment, the pressure in the reactor 13 is set to 0.33 atm by the decompression pump 24 . Thereby, the reaction temperature can be lowered by about 70° C. compared with the decarboxylation reaction in the atmospheric pressure environment.

In this way, carbon dioxide is produced by decarboxylating limestone, which is the main component of the refined cement powder M, in the reactor 13, and the amount of carbon dioxide flowing through the gas circulation line 11 increases. The gas G containing carbon dioxide corresponding to the amount of carbon dioxide produced in the reactor 13 is recovered in a carbon dioxide recovery line 22, which will be described later.

The separator 14 separates (solid-gas separation) the gas G containing carbon dioxide flowing through the gas circulation line 11 from the quicklime (CaO) generated in the reactor 13 and unreacted cement raw powder M. The separated quicklime (CaO) and unreacted cement raw material refined powder M are sent to the cement manufacturing apparatus 30 and utilized as cement raw material refined powder M.

In the gas circulation line 11, the second heat exchanger 15 separates the carbon dioxide-containing gas G flowing through the gas circulation line 11 between the upstream side and the downstream side across the position where the carbon dioxide recovery line 22 is connected. heat exchange. Specifically, gas G containing carbon dioxide at about 750° C. that has undergone a decarboxylation reaction in the reactor 13, and the rest of the gas G containing carbon dioxide partially recovered in the carbon dioxide recovery line 22 on the downstream side. and a gas G containing carbon dioxide at a relatively low temperature, for example, about 300°C. As a result, the temperature of the gas G containing carbon dioxide that has undergone the decarboxylation reaction in the reactor 13 is lowered to about 300°C, while the temperature of the gas G containing carbon dioxide immediately before entering the first heat exchanger 12 is 600°C. The temperature is increased to

The circulation pump 16 circulates the gas G containing carbon dioxide through the entire gas circulation line 11 . By arranging this circulation pump 16 downstream of the second heat exchanger 15 described above, the gas G containing carbon dioxide, the temperature of which has been lowered to about 300° C. by heat exchange by the second heat exchanger 15, is supplied to the circulation pump. 16, it is possible to prevent the circulation pump 16 from being damaged or deteriorated due to the inflow of high-temperature gas of 500° C. or higher, for example.

The carbon dioxide recovery line 22 is connected to the downstream side of the circulation pump 16, and gas G containing high concentration carbon dioxide is recovered therefrom. The amount of the gas G containing carbon dioxide recovered in the carbon dioxide recovery line 22 (amount recovered per unit time) is, for example, the amount of carbon dioxide produced by the decarboxylation reaction of the refined cement raw powder M in the reactor 13. It is adjusted to be the same as the amount of production (amount of production per unit time). Thereby, the flow rate of the gas G containing carbon dioxide flowing through the gas circulation line 11 is kept constant.

The gas G containing high-concentration carbon dioxide recovered outside the system of the gas circulation line 11 through the carbon dioxide recovery line 22 has a carbon dioxide concentration of 95 vol % or more, for example, a carbon dioxide concentration of 100 vol %. By performing a decarboxylation reaction of limestone contained in the cement raw material refined powder M in the reactor 13, gas G containing such a high concentration of carbon dioxide can be obtained.

The reaction temperature lowering means 23 is provided, for example, in the middle of the carbon dioxide recovery line 22 connected to the gas circulation line 11 . In this embodiment, a decompression pump 24 capable of decompressing the reactor 13 via the gas circulation line 11 is provided as the reaction temperature lowering means 23 . By reducing the pressure in the reactor 13 below the atmospheric pressure with such a pressure reducing pump 24, the reaction temperature of the decarboxylation reaction of limestone contained in the cement raw material refined powder M can be lowered.
In addition to connecting to the carbon dioxide recovery line 22, the decompression pump 24 that constitutes the reaction temperature lowering means 23 can be connected to any location in the gas circulation line 11 as long as the reactor 13 can be decompressed. can.

(Carbon dioxide production method)
The carbon dioxide production method of the present invention using the carbon dioxide production apparatus 10 configured as above will be described.
FIG. 5 is a flow chart showing step by step the carbon dioxide production method of the present invention.
When producing high-concentration carbon dioxide of 95 vol % or more using the carbon dioxide production apparatus 10 , first, the gas G containing carbon dioxide is circulated through the gas circulation line 11 by the circulation pump 16 .

Further, from the preheater 31 of the cement manufacturing apparatus 30, for example, cement raw material refined powder (produced raw material powder) M heated to about 750° C. is supplied to the gas circulation line 11 through the raw material powder supply line 21. . Also, the pressure reducing pump 24, which is the reaction temperature lowering means 23, is operated to reduce the pressure in the reactor 13 through the gas circulation line 11 to, for example, about 0.33 atm.

Then, in the first heat exchanger (heat exchanger) 12 formed in the bleed duct 41, which is the high temperature atmosphere field H provided in the cement manufacturing apparatus 30, the high temperature bleed gas C2 flowing through the bleed duct 41 and the gas circulation Heat exchange is performed with the gas G containing carbon dioxide flowing through the line 11, and the temperature of the gas G containing carbon dioxide entering the reactor 13 is heated to, for example, about 850° C. (heating step S1).

In addition to the extraction duct 41 connecting the clinker cooler 33 and the calciner 34, the high-temperature atmosphere field H in which the first heat exchanger 12 is provided includes high-temperature parts in the cement manufacturing apparatus 30, such as the cement kiln 32 and the clinker cooler. At least one of 33, preheater 31, and calcining furnace 34 may be used.

Next, in the reactor 13, the cement raw material refined powder M is heated using the gas G containing carbon dioxide heated in the heating step S1 as a heat source. Cement raw material refined powder M is heated to, for example, about 850° C. to 900° C. by gas G containing high-temperature carbon dioxide. As a result, limestone (CaO ₃ ), which is the main component of the refined cement powder M, produces carbon dioxide through a decarboxylation reaction (reaction step S2).

The reactor 13 is decompressed to, for example, about 0.33 atm by a decompression pump 24 that is a reaction temperature lowering means 23 . As a result, the reaction temperature at which limestone decarboxylation occurs is lowered to about 823° C. (see FIG. 4). Due to the reduced pressure by the decompression pump 24, the decarboxylation reaction proceeds even at about 850° C., which is lower than the reaction temperature of 893° C. at atmospheric pressure, and limestone, which is the main component, is reduced to carbon dioxide. and quicklime (CaO).

When the pressure in the reactor 13 is reduced by the reaction temperature lowering means 23, the pressure in the reactor 13 is preferably in the range of 0.1 atm or more and less than the atmospheric pressure (1 atm). When the reaction pressure of the decarboxylation reaction of limestone contained in the cement raw material refined powder M is equal to or higher than the atmospheric pressure, the reaction temperature of the decarboxylation reaction becomes at least 893° C. Even if the gas G containing carbon is heated, the temperature rise may be insufficient, and the decarboxylation reaction may not proceed.
On the other hand, if the reaction pressure of the decarboxylation reaction of the cement raw material refined powder M is 0.1 atm or less, the reaction temperature will drop, but at such a low temperature, the reaction rate will drop significantly, so carbon dioxide will be generated per unit time. It is not practical because an increase in the amount cannot be expected.

In the reactor 13, limestone (CaCO ₃ ), which is the main component of the refined cement powder M, undergoes a decarboxylation reaction from the outside to the inside of each particle. For this reason, with each particle of limestone (CaCO ₃ ), as the reaction time elapses, the reacted substance (CaO) accumulates on the outside of the particle, and the carbon dioxide generated from the unreacted CaCO ₃ on the center side , passes through this reacted substance (CaO) and is released to the outside of the particles. Thus, each particle of CaCO ₃ slows down as the reaction time elapses.

The reaction rate of such decarboxylation reaction of CaCO ₃ particles is shown by the following equation (7).
K=(1−X) ^2/3 ×A・exp(−E/ _RGT )×{1−(P _All・P _CO2 )/P _{CO2_eq} }…(7)
K: reaction rate [1/s]
A: 2.2×10 ⁸ [1/s]
E: 2.0×10 ⁵ [J/mol]
R _G : gas constant 8.314
T: Temperature [K]
P _All : Total pressure [atm]
P _CO2 : CO ₂ partial pressure [atm]
P _{CO2_eq} : Equilibrium _CO2 partial pressure [atm]
X: reaction rate

This equation (7) shows the reaction rate when the CaCO ₃ particles are spherical, and considering the effect of carbon dioxide gas boundary film diffusion, the equilibrium partial pressure of carbon dioxide at a predetermined temperature is obtained, and the reactor It is corrected by the ratio of the carbon dioxide partial pressure in 13 and the product of the total pressure. The reaction amount was calculated by multiplying the reaction rate coefficient and the residence time in the reactor 13 . The temperature dependence of the equilibrium partial pressure can be measured using a thermobalance or the like.

In such a reaction step S2, the amount of carbon dioxide produced is within a calculated maximum value ±10% based on the internal pressure of the gas circulation line 11 and the temperature of the gas G containing carbon dioxide after being heated in the heating step S1. The reaction pressure in the decarboxylation reaction and the supply amount of the cement raw powder (produced raw powder) M to the gas circulation line 11 are controlled so that

The control of the decarboxylation reaction in the reaction step S2 will be described below.
For example, when a portion of limestone powder such as cement raw material refined powder M is taken from a cement manufacturing process such as the cement manufacturing apparatus 30 shown in FIG. , it can be assumed that the temperature of limestone does not fluctuate greatly. Therefore, the reaction time in the reactor 13 can also be assumed to be constant in a fluidized bed or the like, so the items to be considered are the amount of limestone input, the pressure (or CO2 partial pressure), and the gas containing carbon dioxide flowing through the reactor 13. G is the gas temperature.

The inventors of the present invention have determined the total pressure (or CO ₂ partial pressure) of the gas G containing carbon dioxide and the temperature of the gas G containing carbon dioxide after being heated in the first heat exchanger (heat exchanger) 12 and, depending on the temperature, the reaction pressure (or _CO2 partial pressure) of the decarboxylation reaction, which is the production condition to maximize the carbon dioxide production (or _CO2 concentration) at any given time, and the limestone A method of controlling the decarboxylation reaction in the reactor 13 was found by determining the amount of powder to be charged in advance by chemical engineering calculations.

First, by actual measurement or calculation in advance, an approximate curve is created using the least squares method from the relationship between the amount of limestone input and the amount of carbon dioxide produced for each reaction pressure. Then, the maximum amount of carbon dioxide produced under each condition and the amount of limestone input at that time are obtained. In addition, it may be determined from the relationship between the reaction rate of limestone and the amount of carbon dioxide produced, the relationship between the reaction rate of limestone and the amount of limestone input, the temperature after the decarboxylation reaction, and the reaction rate of limestone.

As a calculation example showing such a relationship, FIG. 6 shows a graph of the relationship between the amount of carbon dioxide produced and the amount of limestone input. Also, FIG. 7 shows a graph of the relationship between the limestone reaction rate and the amount of carbon dioxide produced. Further, FIG. 8 shows a graph of the relationship between the limestone reaction rate and the amount of limestone input. Further, FIG. 9 shows a graph of the relationship between post-reaction temperature and limestone reaction rate. In these calculation examples, the reaction pressure is set to 0.15 atm, 0.20 atm, 0.25 atm, and 0.30 atm, respectively, and carbon dioxide having a concentration of 100% is circulated in the gas circulation line. ing.

Next, under conditions such as constant heat exchange performance and constant enthalpy of carbon dioxide, the maximum amount of carbon dioxide produced and the amount of limestone input at that time are determined for each temperature of carbon dioxide. The resulting values are plotted on a graph of limestone input versus maximum carbon dioxide production. At that time, the horizontal axis is dimensionless with the limestone input amount (L) as the standard, and the vertical axis is the value obtained by dividing the maximum carbon dioxide generation amount C by L on a molar basis per unit time (C / L), carbon dioxide The value obtained by dividing the circulation amount R of the gas G contained in the gas circulation line by L is also expressed as (R/L).

FIG. 10 shows a graph of the relationship between carbon dioxide temperature and carbon dioxide flow rate under constant enthalpy. FIG. 11 shows a graph of a calculation example in which the relationship between the maximum amount of carbon dioxide produced and the amount of limestone input at that time is plotted for each carbon dioxide temperature and (R/L). In the graph of FIG. 11, an approximation curve (hereinafter referred to as isobar) connecting conditions with the same total pressure is created. Also, an approximation curve (hereinafter referred to as an isotherm) connecting conditions with the same carbon dioxide temperature is created.

In addition, in creating the graph shown in FIG. 11, limestone at 750 ° C. is used so that carbon dioxide after heat exchange flowing in the gas circulation line is 900 ° C. and 12000 L / min (converted to 0 ° C.). Assuming a reaction time of 10 seconds in the reactor 13 where the decarboxylation reaction occurs, the gas temperature after heat exchange is 850° C., 875° C., 900° C., 925° C., and 950° C. under the condition of constant enthalpy. Furthermore, under the conditions of total pressure of 0.15 atm, 0.20 atm, and 0.30 atm, the amount of carbon dioxide produced, reaction rate, and after reaction when the amount of limestone input is changed stepwise from 0 kg / hour to 100 kg / hour From the temperature, the amount of limestone input that produces the maximum amount of carbon dioxide under each condition is determined. FIG. 12 shows a graph of a calculation example in which the relationship between the maximum carbon dioxide production amount and the limestone input amount at that time is plotted for each temperature and flow rate of carbon dioxide and reaction pressure.

Then, as shown in FIG. 13 (an enlarged view of the main part of the graph of FIG. 12), the desired amount of carbon dioxide generation and the value of the assumed limestone input amount are shown in the graph of the limestone input amount and the maximum carbon dioxide generation amount. Draw a point X. Let points A, B, C, and D be points of intersection of the two isobars surrounding this point X and the two isothermal lines.

Rectangular areas partitioned by line segments AB, BC, CD, and AD connecting the intersections A, B, C, and D thus created, respectively, are shown in FIG. Divide into minutes. The finer the number of divisions, the higher the calculation accuracy. Then, grid-like auxiliary lines (one-dot chain lines in FIG. 14) connecting the division points are created.

Then, the distance between the point X indicating the desired amount of carbon dioxide production and the assumed amount of limestone input, and the isobar and isothermal line surrounding this point X are examined, and the point X is divided proportionally according to the distance. The satisfying reaction pressure and carbon dioxide temperature can be determined.

If the line segments AB, BC, CD, and AD deviate significantly from the isobars and isothermal lines, narrowing the intervals between the isobars or isothermal lines can improve the calculation accuracy.
As described above, by calculating in advance the reaction pressure in the decarboxylation reaction and the supply amount of the cement raw powder (raw raw material powder) M to the gas circulation line 11, the amount of carbon dioxide produced can be maximized. It is possible to efficiently generate carbon dioxide by decarboxylation reaction.

In the calculation example in the reaction step S2 shown in FIGS. 12 and 13, the reaction pressure and the carbon dioxide temperature are calculated so as to satisfy the production amount of carbon dioxide of 33 L/min and the limestone input amount of 30 kg/h.
Carbon dioxide temperature (925 x 5 + 900 x 5) / 10 = 912.5 (°C)
The reaction pressure is (0.30 × 4 + 0.25 × 6) / 10 = 0.27 (atm)
Then, the amount of carbon dioxide generated: 32.9 L / min, the amount of limestone input: 30.9 kg / hour, and when the amount of carbon dioxide generated is set to 33 L / min and the amount of limestone input is set to 30 kg / hour, -0 It can be calculated with an error of .5%, +3.0%.

The prediction accuracy can be further improved by increasing the number of divisions until the point X is passed. The figure created in such an embodiment is dimensionless with the limestone input amount (L) as a reference of 19.24 kg / hour (192.2 mol / hour), so that the same one as in FIG. 11 can be obtained. can be done.

In the gas circulation line 11 on the downstream side of the reactor 13, a gas G containing carbon dioxide, quicklime produced by the decarboxylation reaction, unreacted cement raw powder M remaining without reacting in the reactor 13, etc. It flows towards separator 14 .

In addition, in such control, fluctuations in the amount of carbon dioxide produced due to fluctuations in the temperature of the high temperature field and the output of the decompression pump in actual operation, Considering the amount of production and cost performance, as shown in FIGS. 15 and 16, if the amount of limestone input is controlled to be within ±10% of the maximum amount of carbon dioxide produced in the calculation, the same effect can be obtained. can be obtained, it is preferable to control the amount of carbon dioxide produced to be within the calculated maximum value ±10%.

In the separator 14, gas (gas) G containing carbon dioxide is separated from powders (solids) such as quicklime produced by the decarboxylation reaction and unreacted cement raw material refined powder M (solid-gas separation step S3 ). The quicklime (CaO) separated by the separator 14 and the unreacted cement raw material refined powder M are introduced into the extraction duct 41, sent to the calciner 34 of the cement manufacturing apparatus 30, and effective as the cement raw material refined powder M. used.

The temperature of the gas G containing carbon dioxide that has been solid-gas separated through the separator 14 is about 750° C., and if it enters the circulation pump 16 on the downstream side of the gas circulation line 11 as it is, there is a concern that the circulation pump 16 will be damaged by heat. be. In this embodiment, the second heat exchanger 15 is arranged between the circulation pump 16 and the separator 14 . Then, the gas G containing carbon dioxide at about 750° C. flowing into the second heat exchanger 15 has a temperature lowered to about 300° C. on the downstream side of the connection position of the carbon dioxide recovery line 22, and the gas circulation line 11 heat exchange with gas G containing carbon dioxide flowing through.

As a result, the temperature of the carbon dioxide-containing gas G flowing into the circulation pump 16 is lowered to, for example, about 300° C., preventing the circulation pump 16 from being damaged or deteriorated due to heat. On the other hand, the gas G containing carbon dioxide flowing into the first heat exchanger 12 by circulation is heated to, for example, about 600° C. by the second heat exchanger 15, and the gas containing carbon dioxide in the first heat exchanger 12 It helps to reliably raise the temperature of G to about 850°C.
The second heat exchanger 15 does not necessarily need to be provided, and can be omitted depending on the characteristics of the circulation pump 16 and the temperature of the gas G containing carbon dioxide flowing into the first heat exchanger 12 .

Part of the gas G containing carbon dioxide that has passed through the circulation pump 16 is recovered outside the system of the gas circulation line 11 from the carbon dioxide recovery line 22 connected to the gas circulation line 11 (recovery step S4). The concentration of carbon dioxide in the gas G containing carbon dioxide recovered via the carbon dioxide recovery line 22 is 95 vol % or more, for example 100 vol %.

In the recovery step S4, the amount of the gas G containing carbon dioxide recovered through the carbon dioxide recovery line 22 (the amount recovered per unit time) is, for example, the decarboxylation reaction of the refined cement raw powder M in the reactor 13. It is adjusted to be the same as the amount of carbon dioxide produced by (the amount of production per unit time). Thereby, the flow rate and pressure of the gas G containing carbon dioxide circulating in the gas circulation line 11 can be kept constant.

Thereafter, the gas G containing carbon dioxide that has not been recovered in the carbon dioxide recovery line 22 is heated to, for example, about 600° C. by the second heat exchanger 15, and then the above steps are repeated from the heating step S1.

As described above, according to the carbon dioxide production apparatus 10 and the carbon dioxide production method using the same of the present invention, the gas G containing carbon dioxide is circulated in the gas circulation line 11, and the carbon dioxide is produced in the high-temperature atmosphere field H. 95 vol by heating the gas G containing the % or more of high concentration carbon dioxide can be continuously and efficiently generated. High-concentration carbon dioxide can be directly liquefied, and carbon dioxide after recovery can be efficiently transported and stored.

When the decarboxylation reaction is performed, the reactor 13 is decompressed by a reaction temperature lowering means such as a vacuum pump to lower the reaction temperature, thereby reducing the temperature to a high temperature close to 900° C. like the decarboxylation reaction in an atmospheric pressure environment. Since there is no need to do so, the gas G containing carbon dioxide is heated using the high temperature atmosphere field H of the cement manufacturing apparatus whose maximum temperature is about 800 to 850 ° C., and this gas is used as a heat source to convert the cement raw material refined powder M to carbon dioxide. Carbon can be produced at low cost.

In addition, according to the present invention, the gas G containing a high concentration of carbon dioxide does not contain carbon dioxide generated by burning fossil fuels such as coal, petroleum, and natural gas as a generation source. Efficient high-concentration carbon dioxide that can be applied to food ingredients, etc., without concerns about impurities harmful to the human body and plants such as volatile organic compounds (VOC), carbon monoxide, nitrogen oxides, and sulfur oxides. can be manufactured.

Furthermore, the first heat exchanger for heating the gas G containing carbon dioxide, which serves as a heat source for decarboxylating the limestone contained in the cement raw material refined powder M, is provided with a solid such as cement raw material refined powder containing limestone. Since the powder (powder) does not flow into the first heat exchanger (heat exchanger) 12, the solid (powder) does not adhere to the first heat exchanger (heat exchanger) 12 and clog the flow path. Carbon dioxide can be produced.

According to the carbon dioxide production method of the present invention, in the reaction step, the amount of carbon dioxide produced is maximized based on the internal pressure of the gas circulation line 11 and the temperature of the gas containing carbon dioxide after being heated in the heating step S1. By controlling the reaction pressure in the decarboxylation reaction and the supply amount of the raw material powder to the gas circulation line 11, carbon dioxide can be produced with maximum efficiency. As a result, a large amount of high-concentration carbon dioxide can be produced at low cost.

(Method for designing carbon dioxide production equipment)
In the method for designing a carbon dioxide production apparatus of the present invention, the amount of carbon dioxide produced is within a maximum value of ±10% based on the internal pressure of the gas circulation line and the temperature of the gas containing carbon dioxide after being heated in the heating step. The reaction pressure in the decarboxylation reaction and the supply amount of the raw material powder to the gas circulation line are determined so as to be within the range, and the carbon dioxide production apparatus is designed based on this determination.

Specifically, in designing the carbon dioxide production apparatus, based on the carbon dioxide production method described above, the capacity of the vacuum pump, which is the reaction temperature lowering means, is set so that the reaction pressure becomes a predetermined reaction pressure. By setting the heating temperature required for heat exchange of gas containing carbon dioxide in the heat exchanger (heat exchanger), the high temperature atmosphere field H for installing the first heat exchanger is selected, etc. It is possible to design a carbon dioxide production apparatus that maximizes the production efficiency of

Although several embodiments of the invention have been described above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 10... Carbon dioxide production apparatus 11... Gas circulation line 12... 1st heat exchanger (heat exchanger)
DESCRIPTION OF SYMBOLS 13... Reactor 14... Separator 15... Second heat exchanger 16... Circulation pump 21... Raw material powder supply line 22... Carbon dioxide recovery line 23... Reaction temperature lowering means 24... Decompression pump 25... Reaction vessel 31... Preheater 32... Cement kiln 33... Clinker cooler 34... Calcination furnace H... High-temperature atmosphere field G... Gas containing carbon dioxide M... Cement raw material refined powder

Claims (6)

Equipped with carbon dioxide production equipment, calciner and cement kiln,
The carbon dioxide production apparatus includes a gas circulation line for circulating a gas containing carbon dioxide, a heat exchanger, a reactor, and a separator sequentially arranged in the gas circulation line, and a raw material connected to the gas circulation line. A powder supply line, a carbon dioxide recovery line, and a reaction temperature lowering means,
The heat exchanger exchanges heat between the gas circulation line and a high-temperature atmosphere field having a temperature higher than the temperature of the gas circulation line,
The raw material powder supply line is connected between the reactor and the heat exchanger or connected to the reactor to introduce raw material powder for carbon dioxide generation into the gas circulation line,
The reactor brings the raw material powder into contact with the gas containing carbon dioxide heated by the heat exchanger to produce carbon dioxide through a decarboxylation reaction,
The separator separates the raw material powder and the gas containing carbon dioxide,
The reaction temperature lowering means lowers the reaction temperature of the decarboxylation reaction in the reactor by a decompression pump that decompresses the reactor,
The carbon dioxide recovery line recovers the gas containing carbon dioxide having a carbon dioxide concentration of 95 vol% or more outside the system of the gas circulation line,
The calcining furnace heats the raw material powder separated by the separator,
The cement kiln heats the raw material powder heated in the calciner to generate cement clinker. Further comprising a clinker cooler, a preheater, and a bleed duct connecting the clinker cooler and the calciner, wherein the high-temperature atmosphere field comprises the cement kiln, the clinker cooler, the preheater, the calciner, and the bleed. 2. The cement manufacturing apparatus according to claim 1, comprising at least one of ducts. A cement manufacturing method using the cement manufacturing apparatus according to claim 1 or 2,
A heating step of heating the gas containing carbon dioxide in the heat exchanger in the high-temperature atmosphere field;
a reaction step of bringing the raw material powder into direct contact with the gas containing carbon dioxide heated in the heating step and heating it to cause a decarboxylation reaction to produce carbon dioxide;
a solid-gas separation step of separating the raw material powder and the gas containing carbon dioxide;
a recovery step of recovering an amount of the gas containing carbon dioxide corresponding to the amount of carbon dioxide produced in the reaction step, and refluxing the remaining gas containing carbon dioxide to the gas circulation line;
a calcining step of heating the raw material powder separated in the solid-gas separation step in the calcining furnace;
and a cement clinker producing step of heating the raw material powder heated in the calcining step in the cement kiln to produce cement clinker. In the reaction step, based on the internal pressure of the gas circulation line and the temperature of the gas containing carbon dioxide after being heated in the heating step, the amount of carbon dioxide produced is within a maximum value of ±10%. 4. The cement production method according to claim 3, wherein the reaction pressure in said decarboxylation reaction and the supply amount of said produced raw material powder to said gas circulation line are controlled. 5. The method of manufacturing cement according to claim 3, wherein in the reaction step, the reaction pressure of the decarboxylation reaction is set below atmospheric pressure by the reaction temperature lowering means. The method for designing a cement manufacturing apparatus according to claim 1 or 2,
Based on the internal pressure of the gas circulation line and the temperature of the carbon dioxide-containing gas after being heated by the heat exchanger, the desorption is performed so that the amount of carbon dioxide produced is within the maximum value ± 10%. A method of designing a cement production apparatus, comprising determining a reaction pressure in a carbonation reaction and a supply amount of the produced raw material powder to the gas circulation line, and designing the carbon dioxide production apparatus based on this determination. .

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